Looking back specs of some long standing car/truck models over the last 20 years reveals that there have been remarkable gains in overall efficiency. Most models have experienced huge weight gains, significant displacement increases (many have experienced nearly 50% increases in torque and horsepower) and yet they manage to get equal-to-or-better-than fuel economy.

It shouldn't be too dificult to turn the equations on their head and start applying these technologies to smaller, more fuel efficient engines that achieve the same level of performance as cars from decades gone by. Can you get to 50+ MPG this way? I don't know, but I have a feeling it would be a big leap toward that goal. Of course, it will require discipline from us (consumers) to accept the resulting drop in performance...or perhaps $4-$5/gallon gas is making that decision easier to accept.

I'm still driving my 1998 VW Jetta TDI (Turbo Diesel Injection) & achieving 50mpg city. It was advertised at 42 city/48 highway. At the time I bought it in 1998 diesel was $.90/gal. I have never at a want of power out of its 90 HP motor.

There is a whole community of people driving these VW diesels (http://www.tdiclub.com/) who have been wondering for years why our diesels are never mentioned in articles regarding the best mpg vehicles on the road.

As many have pointed out, Europe knows the benefits of diesel over gas. The problem in the US is perception. People remember the diesels of the 70's, slow, no acceleration, dirty & noisy. That isn't the diesel of today. But no one has taken up the mantra of the diesel & made an effort to change its perception.

Some tweaks to the EPA regulations & some culture change & the 54.5mpg goal could easily be attained & surpassed in years not decades.

The real culture change needed is the size of US autos. SUV's need to die a dinosaur’s death. Cars need to get smaller, not Smart car small, but definitely a reduction in width & length. Of course this won't be a change people of this country will commit to voluntarily, it needs to be forced on us & on the auto makers. The auto makers will always make what sells & the demand is now for bigger, which always comes at a cost of mpg.

The auto makers already possess technology to make cars get this gas mileage, the problem is that they wouldn't be money makers. Most people would write them off as being too small, dangerous, and dorky. (Interesting the CR-Z is used above as an example: my '89 CRX with outdated technology got better than 40mpg)

I see the government's CAFE regulations as not just pushing scientists to develop game-changing technology, but as a way of forcing the public to do something they don't want to do; namely consume less fuel. If the government wants people to consume more fuel, then they're shooting themselves in the foot and punishing the auto-makers in the process.

So back to the author's original question: what areas will need to be pioneered to make the new CAFE regulations doable? Because it is clear from Auto sales that the majority of Americans would rather pay for more gas than decrease their energy use via a small car, the only way to enable them to have a heart change is for gas prices to take a huge hike. If gas was $8/gal like it is in Europe, Americans would be beating down the doors to buy a 55mpg car and the auto companies would gladly supply.

"Economy and safety do not always attract the huge crowds of buyers. Perhaps that should serve as a reminder to the regulators."

That's exactly why the regulators are doing this. Many, if not most, of the people in the USA seem to be blithely unaware that fossil fuels are finite and are ignorant about the reality of global warming. Of course, there is a good percentage who just don't care if we run out and don't care that the planet will be permanently affected by reduction of species and crop yields.

Engineering magazines in Europe are ALL about global warming, reducing emissions by making everything more efficient and making cars more economical.

With the current record for a gas powered vehicles standing at over 10,000 mpg in the Shell mileage competition you'd have thought engineers in the land of American "Exceptionalism" could get better mileage than the rest of the planet.

I just wonder why people complain about the cost of gas and yet they are driving around with only one person in an F150 pickup. Even if they buy a high performance car like a Mustang - they cannot drive it any faster down the road than anybody else. The speed limit is a barrier for all but a Smart car.

In summary, I pointed out the challenges that will be in the way of meeting this new hurdle. The simple choices are to only require the companies to offer such a vehicle, not for it to be the majority of those sold. Economy and safety do not always attract the huge crowds of buyers. Perhaps that should serve as a reminder to the regulators.

Thanks to everyone for the thoughtful comments and spirited debate. I hadn't mentioned diesel because of the emissions issues, which I think disqualifies it. Separately, there does seem to be a buy-side gating (blocking) factor, which Charles Murray wrote about thoughtfully in his post, California Should Mandate the Purchase of EVs. I can't help but wonder if another oil crisis, a la 1973 (or 79) would get things into gear far quicker than either legislative prodding or technical progress.

There is an inherent problem with the concept of mandating an arbitrary CAFE level, which is that nobody is forcing the public to purchase those vehicles. So by mandating that the car companies produce vehicles that people won't buy, the goal of forcing reliance on public transport comes closer.

Power requirements are set by both vehicle mass and vehicle drag. There are several problems with using lighter materials, the worst problem is that they get expensive, as strength increases and weight decreases. In addition, these materials also (usually) wind up being more suscepable to corrosion damage. So one winter with the Detroit area road salt and the magnesium honeycomb frame members will be a small pile of magnesium chloride salt. Thinner, high strength, steel has a similar, but somewhat slower, failure process. Having ones $35,000 car turn to dust would indeed be a problem.

Reducing drag offers more hope, but will it be possible to produce a car with low enough drag? The lowest drag finish is not that difficult, but the lowest drag shapes may not look anything like what folks wish to buy or drive. That can be a fatal problem. From the technical point of veiw, reducing drag can also get to be quite expensive, and add the weight so painfully removed.

I'd like to mention something not on the six item list of suggested talking points.

We should not neglect the obvious need for sizing vehicles for their primary intended function. Drivers don't need gigantic vehicles for their commute to work or for shopping - we shouldn't be marketing SUV's to every category of vehicle buyer. Auto makers are also addicted to the profits they make on each SUV but by offering more choice in the form of smaller niche vehicles they should be able to sell more new cars, gain more market share.

Smaller lighter vehicles will be the big factor in improving each automakers overall fleet efficiency. Design and marketing will help make the change more palatable for people who are addicted to commanding their own personal tank.

I believe the environmental problem is actually problem of entropy. Any material created by man can be assimilated as fuel and broken down by Nature.

The issue is time:

Nature requires a few billion years to figure out how to do this. Humans are capable of introducing new entropy into the system faster than the system can absorb it.

As a contextual example of this, humans are capable of reducing oxygen. However, if plant life behaved like humans and thus was able to instantly reproduce 100% pure oxygen this oxygen would burn our lungs and we would not be able to accept it.

A few weeks ago, Ford Motor Co. quietly announced that it was rolling out a new wrinkle to the powerful safety feature called stability control, adding even more lifesaving potential to a technology that has already been very successful.

It won't be too much longer and hardware design, as we used to know it, will be remembered alongside the slide rule and the Karnaugh map. You will need to move beyond those familiar bits and bytes into the new world of software centric design.

People who want to take advantage of solar energy in their homes no longer need to install a bolt-on solar-panel system atop their houses -- they can integrate solar-energy-harvesting shingles directing into an existing or new roof instead.

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